Twine

ABSTRACT

A twine having a maximum knot strength of 10 percent higher than the knot strength of earlier twines comprising a core of extensible, synthetic, plastic filaments with an extensible cover wound about said core is achievable by twisting together a resilient synthetic (particularly, polypropylene and also polyolefin, an acrilic resin, nylon, polymers of halogenated hydrocarbons, polyesters or similar resinous materials having high tensile strength and resiliency in the direction of orientation with breaking tenacity of 3.5-7 gpd.) film oriented in the longitudinal direction and an extensible paper such as Kraft or tissue type having a stretch in the machine direction of 4 percent or more. The paper and film components of the twine disclosed may be reinforced with synthetic filament yarn.

United States Patent [191 Catlos [4 1 May 29, 1973 v [73] Assignee:

[ 1 TWINE [75] Inventor: Peter V. Catlos, Huron Park, On-

tario, Canada Ferplas Industries Limited, Huron Park, Ontario, Canada 22, Filed: Nov. 5, 1970 21 Appl.No.: 87,295

[52] U.S.Cl. ..57/155,57/150, 57/151,

57/165, 57/167 I [51] Int. Cl ..D02g 3/02, D02g 3/04, D02g 3/08 [58] Field of Search ..57/139, 140, 151, 57/154, 155, 165,167,150

[ 56] References Cited UNITED STATES PATENTS 3,543,504 12/1970 Goy ..57/l55 UX 2,418,215 4/1947 Lambert .....57/l55 UX 2,961,011 11/1960 Brown.....- i ..57/15l X 3/1964 ...57/l55 X Lefevre et a1.....

10/1967 Portetal. ..57/l5lX 6/1969 Orser ..57/lSlX Primary Examiner Donald E. Watkins Attorney-Philip T. Mitches [5 7] ABSTRACT A twine having a maximum knot strength of 10 percent higher than the knot strength of earlier twines comprising a core of extensible, synthetic, plastic filaments with an extensible cover wound about said core is achievable by twisting together a resilient synthetic (particularly, polypropylene and also polyolefin, an acrilic resin, nylon, polymers of halogenated hydrocar bons, polyesters or similar resinous materials having high tensile strength and resiliency in the direction of orientation with breaking tenacity of 3.5-7 gpd.) film oriented in the longitudinal direction and an extensible paper such as Kraft or tissue type having a stretch in the machine direction of 4 percent or more. The paper and film components of the twine disclosed may be reinforced with synthetic filament yarn,

10 Claims, 3 Drawing Figures TWINE This invention relates to twine.

Many different types of twine are known. These twines are generally formed from either natural fibers for example manilla, jute, cotton, hemp and sisal fibers and kraft paper or synthetic fibers, for example rayon, nylon, polypropylene. In most instances, these materials are used alone but, for example, in US. Pat. No. 1,320,920 issued on Nov. 4, 1919 to G.L. Rice, natural fibers are wrapped in a paper covering. Few, if any advantages are obtained by wrapping natural fibers in paper and the increased cost of such a twine is not justi- U.S. Pat. No. 2,826,416 issued to American Sisalcraft Corporation on Nov. 25, 1958 describes a twine that uses a combination of kraft paper and glass fibers. This twine may be quite strong but it is also relatively stiff and when tied and placed under tension it tends to be brittle, very weak at the knot and unsuitable for use in binders and balers.

Twines formed wholly from synthetic fibers are known and although they have adequate strength to replace natural fiber twines, they also have serious shortcomings when used in binders and balers. Synthetic twines lack sufficient bulk and knot holding ability for use in balers and binders.

' 1.1.5. Pat. No. 3,418,799 describes a twine comprising a core of extensible, synthetic, plastic filaments and an extensible cover wound about said core. This twine gives excellent results but I have now found that a twine having a maximum knot strength percent higher than the maximum knot strength of my previous twine can be obtained-by together a resilient synthetic film oriented in the longitudinal direction and an extensible paper. Knot strength is defined as the ratio of the breaking strength at the knot to the breaking strength when not knotted.

The extensible paper can be of the kraft or tissue type having a stretch in the machine direction of 4 percent or more. This paper can be natural, bleached, colored, resin impregnated, wet strength processed or finished in other way. The extensible paper is normally available in mill size rolls, which can be slit, in the well known manner of the art, into narrow strips to be used to make the twine of the present invention. Preferred paper is that sold under the trademark Clupak.

The synthetic oriented film can be of a polyolefin, an acrylic resin, nylon, polymers of halogenated hydrocarbons, polyesters or similar resinous material having a relatively high tensile strength in the direction of orientation and relatively high resiliency, so providing for the desired elastic recovery under stress. Preferred film is that having a breaking tenacity of 3.5 to 7 gpd. The preferred resin used to make the film is polypropylene. The film may be cast in the form of a sheet and slit to the desired width or' may be extruded in the desired widths thus eliminating the need for slitting. Fibrillated films are particularly suited for the production of twine according to this invention because of their flexibility; they result in a twine having high knot strength.

In addition to its two basic components, paper and film, the twine of this invention may be reinforced with synthetic filament yarn. Polyolefin, polyester, acrylic or cellulosic filament yarn is particularly suited for such reinforcement.

The proportion of paper to film will vary according to the desired properties which are to be built into the composite twine. This proportion will affect the range of the following cord characteristics: Tensile strength, knot efficiency, bulk, yield, cost per unit of length, flexibility, as well as numerous other characteristics. A preferred composition having excellent physical properties combined with cheapness is percent by weight paper and 25 percent polypropylene film.

Generally speaking, an increase in the quantity of film will add to the strength of the composite twine but at the same time will add to its cost. On the other hand a paper increase will increase the bulk and knot efficiency of the twine and will lower its cost because it is the less expensive of the two components.

The twisting process may or may not require lubrication, however when lubrication is desirable it has been found that several lubricants are suitable. Water has been found adequate to lubricate wet strength paper (wet twisting). The twine produced by this method is subsequently dried.

Low wet strength paper can be lubricated by mineral oils, glycerines, glycols or emulsified waxes of varying specific gravities.

It has also been found that heating of the paper just before it is fed into the twister makes it more pliable and improves its twisting property.

Most fihns used in the production of composite twine according to this invention have been found to be sufficiently flexible for twisting, but their flexibility can also be increased by the application of heat. The range of such heat treatment must be well below the point at which the molecular structure of the film would be adversely affected. Properly applied, heat can be used to advance the orientation of certain films during the twisting process, for examplefilms made from polyolefins. Such heating, by passing heat to the paper being twisted with the film, can make the paper more pliable as mentioned above.

The twine of the present invention is particularly suitable for use in binders and balers and can be readily knotted with conventional machinery, has adequate bulk, possesses satisfactory resiliency and flexibility and otherwise meets the requirement for an economical replacement for sisal binder and baler twine.

The two components of the twine of this invention are both extensible and have substantially the same rate of elongation. Thus when the twine is placed under stress the synthetic material and the paper material, while having two separate breaking points, have elongation limits which are close enough together that they appear to break simultaneously. This characteristic results in good performance and knotting ability.

The twine of this invention is also substantially water and rot resistant, a feature of significance when used as binder and baler twine. Also,'the twine of this invention has been found to have an improved weight to strength ratio and higher knot efficiency than natural fiber twines.

Methods of making the twine of the present invention include:

a. The composite twine can be manufactured from paper and film strip of the same width with the paper forming the outer layer and the film forming the inner layer or core of the twine. The proportion of the two materials in the twine can be changed by varying the gauge of the paper and the film independently.

b. The composite twine can be manufactured using paper strip that is wider than the film strip in order to provide better coverage of the film by the paper. The proportion of the two materials in the twine can be changed by varying the relative widths of the paper and film or the relative thickness, or both.

c. The composite twine can be manufactured by using film strip which is wider than the paper strip, with the two twisted in a manner giving the composite twine a variegated effect by exposing parts of the film and the paper on the surface of the twine. This construction will impart a higher abrasion resistance to the surface of the twine.

d. The composite twine can be manufactured in combination as described in paragraph c, with the film strip being folded, lapped or crushed such that there is a multiple thickness of film along the central portion of its width. This construction is preferred to one where heavy gauge film is used, since film of a heavy gauge is not as flexible as a number of layers of light gauge film.

e. The composite twine can be made as in any of the above combinations as described in paragraphs a, b, c and d, with the film being spot glued or laminated to the paper before twisting. Such gluing or lamination will create a more positive bond between the film and the paper and will improve the separation strength of the paper from the film during abrasion such as when knotting.

f. The composite twine can be formed by twining a separate twisted cord of synthetic film with a separate twisted cord of extensible paper. In this case the film and the paper are not in the laminated relationship as are materials in the twines described in paragraphs a, b, c, d and e, but are the two plies of the composite twine.

g. A composite twine can also be formed with the film being the outside liner and the paper being the inside liner or core of the twine.

h. A composite twine can also be made by using several layers of film and paper.

i. A composite twine can also be formed by twisting a paper which has been coated with a film-forming synthetic resin.

k. A composite twine can also be made by twisting extensible paper and oriented film around a core of synthetic filament yarn, with all three components having compatible limits of elongation.

The present invention will now be described by way of example with reference to the following drawings and examples in which:

FIG. 1 shows a system for producing the composite paper plastic yarn.

FIG. 2 is a perspective showing the yarn partly untwisted.

FIG. 3 showing an alternative embodiment of the yarn partly untwisted.

EXAMPLE 1 A strip of 9,000 denier polypropylene film 11 either from sheet material on a roll or, by way of bob 12 made from a resin sold under the trademark Avisun 1014 was twisted by a conventional twine twisting apparatus 15 with a strip of paper 16 sold under the trademark Clupak. This paper is an extensible kraft paper and has received a strength in the machine direction 16 of about 6 percent.

Strips of film and paper were made of the same width as by cutters 20 and 21 but their thickness was such that the paper comprised percent by weight of the produced twine 25. The paper comprised the outer layer of the twine. The produced twine 25 had a knot strength of percent.

EXAMPLE 2 A twine was produced as in Example 1 but the polypropylene film used was that made from a resin sold under the Trade Mark Avisun 4014. This resin differs from Avisun 1014 by not possessing anti-fade constituents.

The resulting twine was of the same high quality as the twine produced in Example I.

Ifthe films are filabrated, FIG. 3; the film may be filabrated into fiber 27 and extruded strands 28, the fiber 21 and strands 28 form the inner core of the twisted twine 25, the outer covering of which is extensible paper 16.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A twine comprising an inner core of a strip fibrillated of film of a resilient synthetic resin oriented at least in the longitudinal direction of the twine and having a standard breaking tenacity of 3.5 to 7 gpd and an outer cover of a strip of extensible paper.

2. A twine as claimed in claim 1, wherein the strip of film is of the same width as the strip of paper.

3. A twine as claimed in claim 1, wherein the strip of paper is of less width than the strip of film.

4. A twine as claimed in claim 1, wherein the film is of a polyolefin, a polyester, an acrylic resin, nylon or other resilient plastic.

5. A twine as claimed in claim 1 in which the resin is polypropylene.

6. A twine as claimed in claim 1, wherein the paper is of the kraft type having a stretch in the machine direction of not less than 4 percent.

7. A twine as claimed in claim 1, wherein the paper and film are reinforced with synthetic yarns or cords.

8. A method of making composite twine comprising placing a strip of synthetic oriented film onto a strip of extensible paper, bonding said strip of film to said strip of paper at least in spots, and thereafter twisting the composite strip.

9. A twine comprising an outer cover of a strip of a resilient synthetic resin oriented at least in the longitudinal direction of the twine and having a standard breaking tenacity of 3.5 to 7 gpd and an inner core of a strip of extensible paper.

10. A twine comprising an inner core of a strip of film of a resilient synthetic resin oriented at least in the longitudinal direction of the twine and having a standard breaking tenacity of 3.5 to 7 gpd and an outer cover of a strip of extensible paper, in which said paper and said film are reinforced with synthetic yarns.

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2. A twine as claimed in claim 1, wherein the strip of film is of the same width as the strip of paper.
 3. A twine as claimed in claim 1, wherein the strip of paper is of less width than the strip of film.
 4. A twine as claimed in claim 1, wherein the film is of a polyolefin, a polyester, an acrylic resin, nylon or other resilient plastic.
 5. A twine as claimed in claim 1 in which the resin is polypropylene.
 6. A twine as claimed in claim 1, wherein the paper is of the kraft type having a stretch in the machine direction of not less than 4 percent.
 7. A twine as claimed in claim 1, wherein the paper and film are reinforced with synthetic yarns or cords.
 8. A method of making composite twine comprising placing a strip of synthetic oriented film onto a strip of extensible paper, bonding said strip of film to said strip of paper at least in spots, and thereafter twisting the composite strip.
 9. A twine comprising an outer cover of a strip of a resilient synthetic resin oriented at least in the longitudinal direction of the twine and having a standard breaking tenacity of 3.5 to 7 gpd and an inner core of a strip of extensible paper.
 10. A twine comprising an inner core of a strip of film of a resilient synthetic resin oriented at least in the longitudinal direction of the twine and having a standard breaking tenacity of 3.5 to 7 gpd and an outer cover of a strip of extensible paper, in which said paper and said film are reinforced with synthetic yarns. 